1. Field of the Invention
The present invention relates to a narcotic antagonist and a medicament for the prevention and treatment of narcotic dependence.
2. Background Art
Narcotics, typically represented by cocaine, have rapidly spread worldwide since the Vietnam War. Because narcotics cause strong dependency, once a user becomes dependent on them, it is difficult for the user to abandon his habitual use of them. Thus, despite great efforts made in many countries for controlling narcotics, any attempts so far have been unsuccessful, and permitted them to further spread worldwide.
Under the above circumstances, various attempts have been made to develop compounds for treating cocaine dependence. For example, certain piperazine derivatives which act on neuroreceptors have been found to have a therapeutic action for narcotic dependence (International Patent Publication (kohyo) No. 4-504859). However, when such a piperazine derivative is used at a concentration high enough to cure narcotic dependence, it often happens that the derivative also strongly exhibits other activities, giving adverse side effects. Therefore, substances that strongly act on narcotic receptors are still desired.
In view of the foregoing, the present inventors carried out extensive screenings using narcotic antagonism as an index and found that the compounds represented by the following formula (1) described below possess strong narcotic antagonism and thus are useful as preventive and therapeutic agents for narcotic dependence. The present invention was accomplished based on this finding.